The present invention relates generally to a transport refrigeration system employing a current sensor used to detect unacceptably high levels of mechanical vibrations associated with an electrical motor drive shaft based device, such as a scroll compressor.
A current sensor positioned on a power line leading to a system component in a transport refrigeration product monitors current in the component. In prior transport refrigeration products, the current sensor monitors current to determine system operation states and to perform self-diagnostic tests to determine if a system component is working properly. If a component is not working properly or is turned off, the system current is less than what the system current would be if the component is working properly or is turned on. When the current sensor detects this, the current values are displayed on a display/keypad interface to indicate the system operating state to the system user.
Vibration within a compressor can be indicative of a problem with the compressor or with the overall refrigeration system. To date, there has been no simple and effective way of identifying undue levels of vibration. As an example, problems within the compressor, such as a broken mounting bracket, can result in mechanical vibrations increasing to high levels. It would be desirable that a warning signal be sent in the event that such levels are occurring.
Problems such as mentioned above are particularly desirable detected early on in transport refrigeration systems. A transport refrigeration system is typically utilized on a vehicle transporting refrigerated cargo, such as frozen foods and perishable cargo. If this system is associated with a failing compressor, the entire cargo could be lost.
Applicant has recognized that high vibration in an electrical motor driven shaft based device will result in detectable current peaks. The present invention relates to a transport refrigeration system employing a current sensor used to detect unacceptably high levels of mechanical vibrations associated with an electrical motor driven shaft based device, and in particular a compressor employed as part of a transport refrigeration system.
A power source supplies power to the compressor of a transport refrigeration system. A current sensor positioned on at least one of the power line legs monitors current draw associated with the compressor. Compressor vibrations force stress on the compressor motor shaft, directly influencing the current draw. As vibrations in the compressor increases, the current draw associated with the compressor increases. By monitoring the current draw associated with the compressor, unacceptably high levels of mechanical vibrations resulting from problems in the compressor, such as a broken mounting bracket, can be detected.
The current values monitored by the current sensor are received by a controller. If the current sensor detects a current value exceeding a threshold current value, the controller indicates that the compressor is undergoing excess vibrations. Alternatively, the controller indicates when the current sensor detects a plurality of current peaks exceeding a threshold current value in a time frame. A warning signal or corrective action can then be taken.
Accordingly, the present invention provides a transport refrigeration system employing a current sensor used to detect unacceptably high levels of mechanical vibrations associated with a compressor. Preferably, the system is utilized with a scroll compressor used in a transport refrigeration system.
These and other features of the present invention will be best understood from the following specification and drawings.